There has been increasing interest in digital TV due to the greater availability of low cost digital hardware and memories. The digital TV allows the user to reformat the incoming video signals. For example, in a digital TV provided with a pix-in-pix or pip feature, an auxiliary or secondary video signal SVS (e.g., from the VCR second detector) defines a small picture on the display screen which is overlaid on a full picture defined by a main or primary video signal PVS (e.g., from the TV second detector).
Typically, the secondary video signal SVS is sampled and digitized at instants determined by a sampling clock signal. The digital samples representing the secondary video signal SVS are then subsampled, both horizontally and vertically, to develop a stream of samples which represent a reduced size image. For a 3-to-1 reduction in the picture size, every third sample and every third line is saved, and the intermediate samples and lines are discarded.
The digital samples taken during one field or frame of the secondary video signal SVS are stored in a memory. These samples are sequentially read out from the memory using a clock signal which is desirably related to the display deflection signal (e.g., horizontal and vertical synchronizing signal components of the primary video signal PVS). The samples read out from the memory are converted into an analog signal SVS' representative of the reduced-size secondary picture. A video output switch, having input terminals coupled to receive the primary video signal PVS and reduced-size secondary video signals SVS', applies an appropriate one of the two input signals to a display device in response to a fast switching signal FFS to produce a small picture within a large picture. U.S. patent application of McNeely et al., Ser. No. 087,060, and entitled "MULTIPLE INPUT DIGITAL VIDEO FEATURES PROCESSOR FOR TV SIGNALS" describes an illustrative pix-in-pix TV receiver.